Field of the Invention
The present invention relates to a vibration-type driving apparatus, and in particular, to a configuration including a vibration absorber in a vibration-type driving apparatus that excites vibrations in a vibrator to give a driving force using the vibration energy.
Description of the Related Art
In general, vibration-type driving apparatuses (for example, ultrasonic motors) include a vibrator in which a driving vibration is excited and a driven body that is in pressure-contact with the vibrator, in which the vibrator and the driven body are moved relative to each other using the driving vibration.
What is called an annular vibration-type driving apparatus of such vibration-type driving apparatuses will be described hereinbelow with reference to FIGS. 10 and 11.
FIG. 10 is a cross-sectional view showing the overall configuration of an annular motor. A driven body 2 is in pressure-contact with a vibrator 1 with a pressure spring 3 to generate a frictional force. Reference sign 6 denotes a base.
This frictional force acts as a driving force to drive the driven body 2. The rotational torque of the driven body 2 is transmitted to a shaft 5 via the pressure spring 3 and a disk 4.
FIG. 11 is a perspective view of the annular vibrator 1. The vibrator 1 includes an elastic member 101, a piezoelectric device 102 fixed to one surface of the elastic member 101, and a friction member 103 provided on the other surface of the elastic member 101. A plurality of protrusions 1a are arrayed in the form of saw teeth on the friction member 103 side of the elastic member 101.
The piezoelectric device 102 has an electrode pattern and a power supply unit (not shown), which causes the vibrator 1 to generate a bending vibration in an out-of-plane direction by the application of an alternating signal to the electrode pattern. This causes a high-frequency fine feed motion in the frictional contact surface of the vibrator 1 to drive the driven body 2.
The vibrator 1 has a supporting portion 104 extending from the vicinity of a neutral plane of the out-of-plane bending vibration of the elastic member 101 toward the inner circumference thereof. The supporting portion 104 is placed on the base 6 and is then fixed thereto by caulking.
For such an annular vibration-type driving apparatus, Japanese Patent Publication No. 8-2186 proposes a vibration wave motor shown in FIG. 12 in which an energy loss due to friction between a driving body and an absorber 7 is reduced to enhance the efficiency of the vibration wave motor.
FIG. 12 is a cross-sectional view of the annular vibrator, which has a supporting portion 104 around the outer circumference of an elastic member 101, the lower surface of which is supported by the vibration absorber 7.
By supporting the vibrator 1 with the absorber 7, the solid-borne propagation of a driving vibration generated in the vibrator 1 to an external device can be blocked, and undesired vibrations other than the driving vibration can be suppressed by the damping effect of the absorber 7.
In the case of FIG. 12, since the supporting portion 104 extends from the vicinity of the neutral plane of the out-of-plane direction bending vibration of the elastic member 101, an energy loss due to the friction between the supporting portion 104 and the absorber 7 can be reduced, and thus, an influence on the driving-vibration generation efficiency can be reduced.
To stably obtain the function and effect of the absorber 7 in the vibration wave motor in the related art, as described above, it is necessary to exert an appropriate compressive force to keep the absorber under sufficient strain. However, the related-art example does not give high satisfaction in obtaining a sufficient compressive force.
For example, even with the above configuration of the absorber under the configuration shown in FIG. 10, only an insufficient compressive force can be given by a motor pressing force that the pressure spring 3 generates and the holding force of the caulked portion of the base 6.
Furthermore, caulking causes variations in fixing strength and irregularity depending on positions, resulting in difficulty in stable production.